arm64: dts: imx8mp-venice-gw74xx: fix ksz9477 cpu port

The CPU uplink port on the KSZ9477 is P5 not P6 - fix this.

Fixes: 7899eb6c ("arm64: dts: imx: Add i.MX8M Plus Gateworks gw7400 dts support")
Signed-off-by: Tim Harvey <tharvey@gateworks.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mp-venice-gw74xx.dts

@@ -510,8 +510,8 @@ lan5: port@4 {
 				local-mac-address = [00 00 00 00 00 00];
 			};
 
-			port@6 {
-				reg = <6>;
+			port@5 {
+				reg = <5>;
 				label = "cpu";
 				ethernet = <&fec>;
 				phy-mode = "rgmii-id";